Absorbent products and methods of preparation thereof

ABSTRACT

An improved absorbency material for absorbency applications comprised of a cellulosic fibrous material wherein said cellulosic fibrous material such as pulp is a cold alkali solution treated material at a treatment temperature of less than about 50° C.; a process for improving absorbency and other characteristics of said pulp.

[0001] This invention relates to pulps for absorbent products, moreparticularly this invention relates to novel use of modified pulps forabsorbent products of household and hygienic uses such as diapers,incontinence and catamenial devices and the like and a method forpreparing pulps of outstanding absorbency characteristics.

[0002] More particularly, this invention relates to the novel use ofknown technology—cold alkali extraction—to produce cellulosic pulpshaving altered and novel fiber properties desirable for end-useapplications for absorbent and fluff pulp products.

[0003] Further, this invention relates to the production of the alteredand novel pulps without addition of chemical additives such as sheetdebonders. Still further this invention relates to the production ofpulps having novel, desirable properties achieved without chemicalmodification steps such as crosslinking with chemical crosslinkingagents.

[0004] Moreover, this invention relates to a novel use of a pulp productcharacterized and defined by its properties for suitable end uses ofthese pulps. Accordingly, novel pulp products can be obtained at reducedcost for the respective, economic effectiveness of these pulps whencompared to pulps prepared by the prior art and suitable for the samepurpose.

BACKGROUND FOR THE INVENTION

[0005] With the increasing prominence of disposable items, such asdiapers, paper towels and the like, and in view of the widely prevalentuse of absorbent tissues of various kinds, it has become important toobtain pulps of high absorbency and especially pulps that display highabsorbency upon multiple re-wetting.

[0006] Typically pulps that are used for hygienic absorption purposessuch as baby diapers and the like are constructed with an outside“acquisition” layer, which is a layer of pulp of good bulking propertiesand good absorbency due to relative fiber stiffness. A bulky materialwill contain a high percentage of void spaces or pores. For an absorbentproduct, these pores are used to acquire, transport and store fluid.Longer, stiffer fibers make bulkier air laid webs with more pore volume.Fluids are more easily acquired and transported if pore volume or bulkis high. The “acquisition” layer is positioned between the baby's skinand the absorbent core of the diaper. An “acquisition” layer of propercharacteristics and properties allows the liquid to pass quickly intothe absorbent core upon repeated wettings and at the same time thislayer transmits the liquid into the principal absorbent core that holdsthe liquid. In a similar manner, an incontinent or catamenial device maybe constructed. Further, wound dressing material may be construed in alike manner. These devices are absorbency products which require pulpshaving intensive absorbency properties.

[0007] Still further, absorbent multiply papers such as household towelsmay be constructed of multiple layers or plies including a core layerand thus these plies may be tailored according to the use to which thesegoods are being subjected or for the purpose these are employed.

[0008] Products such as diapers when used with an outside “acquisition”layer and an interior principal absorbent core, are presently desirablyconstructed with the “acquisition” layer made from crosslinked pulpssuch as are illustrated by the following European Patent applications 0427,316 A2 and 0 427,317 A2 all by Herron et al. and U.S. Pat. No.5,137,537 by Herron et al. assigned to Proctor & Gamble Co. Further,Canadian Patent application 2,035,402, by Kokko based on U.S. priorityapplication No. 07/473,404 and assigned to James River Corp. likewisediscloses such pulps.

[0009] Cross-linked pulps are typically prepared usingformaldehyde-based compounds. More recently, polycarboxylic acids,particularly citric acid, have been shown to be effective cross-linkingagents. Cross-linked fibers display excellent wet stiffness. Thecross-links physically restrict the uptake of water into the fiber wall.By doing so, the fiber retains, better than convention fiber, thecharacteristic stiffness of dry fibers. A web of cross-linked fibers,therefore, retains its bulk and pore volume when wet, which enhancesfluid acquisition, especially with repeated wettings or insults.However, chemically cross-linked fibers are considerably more expensivethan fibers which may be employed without any cross-linking. Moreover,pulps employed in prior art processes for cross-linking purposes aregenerally not available in sheeted form (rolls or bales of sheets).

[0010] Although pulps have been bleached under various alkalineconditions, bleaching schedules and bleaching treatment are by now thosetypically employed by prior art. Accordingly, a wide variety of suchschedules are practiced—for the most part employing at least one or morealkaline steps at fairly high temperatures. In such sequences it hasalso been known to employ caustic solutions at lower temperature andthen the same solution is used to bring up the temperature to or greaterthan a boiling point of the solution as shown in Canadian Patent 578,573entitled “Purification of Wood Pulp” granted Jun. 30, 1959. In thispatent the pulps so produced are used for dissolving pulps, i.e., makingcellulose acetate and other chemical derivatives of cellulose. Nodescription has been found concerning the improvements in absorbency,rewetting properties, stiffness of fibers, etc. as described herein forthe pulps as used for the devices or products as illustrated herein.Moreover, the distinction between dissolving pulps and fluff pulp shouldalso be noted.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] With reference to the Drawing herein:

[0012]FIG. 1 is a plan view of a typical baby diaper;

[0013]FIG. 2 is a cross-sectional view of the diaper shown in FIG. 1,along lines 2-2 thereof; and

[0014]FIG. 3 is a schematic self-explanatory presentation of the overallprocess/product improvements.

BRIEF DESCRIPTION OF THE INVENTION

[0015] It has now been found that cold alkali extraction (CAE) of pulpssuch as preferably obtained from coniferous and deciduous trees resultin fibers that have advantageously and unexpectedly improved absorptionproperties. Pulps from other source materials may also be suitable(e.g., bagasse, straw, etc.). By the term “cold” it is meant a caustictreatment not to exceed 60° C. but desirably at a temperature less than50° C. but preferably at a temperature between 15° C. to 40° C. By theterm caustic it is meant sodium hydroxide solutions newly made up or asa solution by-product in a pulp or paper mill operation e.g., hemicaustic white liquor, oxidized white liquor and the like. Further,ammonium hydroxide, and potassium hydroxide and the like may beemployed. However, from a cost standpoint, the preferable causticmaterial is sodium hydroxide.

[0016] The cold caustic extraction is typically at a caustic strength ina range from about 3% to 25%, preferably from about 6%o to 18%, at apulp consistency from about 2% to 25% but desirably from 2% to 10% butpreferably from 3% to 8%. Pulps for high rate, fast absorbingapplications are preferably treated with cold caustic concentrationsfrom 13% to 18%. A wide variety of pulps are suitable such as obtainedby mechanical or chemi-mechanical, sulfite, kraft, pulping rejectmaterials, organic solvent pulps, etc. Both softwood and hardwoodspecies are useful. Softwood pulps are preferred. Among pulps those thathave not been severely bleached are useful, for example pulps with highK numbers (i.e., “potassium permanganate” number; a high K or kappanumber signifies a relatively high residual lignin content) for thepulp. The more heavily bleached pulp will be improved less and alsorequires a weaker alkali treatment. If the pulps are treated in themanner as i will be further disclosed in the specification herein, thenthe resulting fibers are such that these have good bulking, (i.e.,“stiffness” properties) and thus have much improved absorption andrewetting properties making these pulps attractive for a number of uses.These pulps are not only characterized for their improved properties,such as by their ability to absorb and reabsorb water more quickly (thanthe standard untreated pulps) when subjected to multiple rewet tests,but also these pulps are useful for absorbent devices in the principalcore for such device. In fact, the resulting improvements in theabsorption properties are so significant that the products on aneconomical basis may readily compete with the more expensive prior artcross-linked products described in the above-identified patents.

[0017] As mentioned above, the newly discovered pulp preparation haswide applicability to all types of pulp/fiber source materials anddisplays improved properties for each of the pulps/fibers (FIG. 3). Upona cold caustic treatment of the pulp/fibers, these show improvedproperties. For pulps prepared under different pulping conditions orprocesses such as sulfite, pre-hydrolyzed kraft process, conventionalkraft process, organic solvent processes, or BCTMP (bleachedchemi-thermal mechanical pulp), etc., the properties are invariablyimproved. The improved properties have been observed for all pulp andfiber types investigated. The differences, however, exist between pulpsobtained from various wood species starting materials. Surprisingly, theimproved properties are obtained regardless of the wood species whichhave been employed, for example, western hemlock, Douglas fir, Sitkaspruce, Southern pine, Caribbean pine and the like. Other commercialsoftwood species (e.g., firs and spruces) and hardwood species (e.g.,eucalyptus, poplar, beech, aspen, etc.) yield advantageous properties aswell.

[0018] In an advantageous embodiment, it seems that the bestcharacteristics for the obtained pulp have been observed for pulps thatare unbleached or only slightly bleached. Nevertheless, good resultshave also been observed with bleached or more highly bleached pulps. Asa corollary, the more highly bleached is the pulp, the lower is thecaustic strength that is required to obtain the desirable effects.However, the desirable absorbency effects are somewhat less whencompared on a direct basis with cold caustic extracted pulps derivedfrom high K Number unbleached pulps (i.e. the products derived from highK Number pulps are noticeably better).

[0019] With reference to an embodiment, and the drawing herein, atypical construction of a diaper is shown in FIGS. 1 and 2 therein. InFIG. 1 the plan view of the diaper 3 in its open position shows the tabs4 which are a part of a hook or loop component shown as 5 as itscomplementary element.

[0020] In FIG. 2 which shows in cross section along lines 2-2 of FIG. 1the construction features of diaper 3 and with reference thereto fromtop to bottom each element in the cross section 2-2 is described asfollows:

[0021] Item 11 is a thermally-bonded polypropylene coversheet, it istypically carded or spun. Item 12 is an airlaid cellulose acquisitionlayer. Elements 13 are issue webs of a typical basis weight of about 16g/m²; the absorbent core is identified as 14 and is of a fluff and SAP(super absorbent polymer and pulp mixture of a basis weight of, 500-700g/m²). The water barrier, which is a polyethylene sheet has been shownas 16.

[0022] While the above illustration has been for a diaper, other deviceshave been constructed in a similar manner. Further, for a similarabsorbent paper products, the pulps as modified herein show substantialimprovement in product performance on an economical basis. Thus,products such as catamenial and incontinence devices are improved. Othercandidate applications for which the presently disclosed pulps aresuitable are paper towels, sanitary tissue papers, industrial wipes,etc. For the above applications, the modified pulps may be 100% of theimproved pulps as constituent pulps in the product or may be used in theproduct in lesser quantities, i.e., used in various admixtures withother pulp, from about 100% to about 25%.

TEST PROCEDURES

[0023] Whenever these tests have been described, the industry employedstandard test procedure for the test has been used. If any changes inthe procedure have been made, the changes have been describedspecifically.

[0024] For purposes of evaluating the pulps obtained and described bythe present disclosure as well as the invention herein, several testswere used to characterize the desirable fibrous end-use performanceimprovements resulting from the use of cold alkali extraction and todescribe some of the analytical properties of the pulp products. Also,some of the terminology used in discussing the products in the exampleshas been defined.

[0025] A summary of these tests and definitions follows.

[0026] Pulp Analytical Properties

[0027] The K Number or Kappa test is carried out according to TAPPIStandard Method No. T-214-SU71. This test is a measure of residuallignin content in the pulp. The test indicates the relative degree ofresidual lignin content in a pulp as a consequence of pulping and theextent or severity of pulping.

[0028] Pulp brightness is a measure of pulp whiteness with 100% beingthe maximum. Pulp brightness data here are given as ISO brightnessvalues in %. The ISO brightness test is described in Tappi Method NumberT272 (Handsheets) and T525 (Instrumentation) and uses as a measuringdevice a Datacolor 2000 brightness meter.

[0029] Pulp Sheet Properties

[0030] Debonded pulps are fibrous end-use pulps (for example, fluffpulps) that have some chemical agent (debonder) added to inhibitinterfiber bonding (addition of debonder results in a soft pulp sheet).The chemical agents, debonders, are commercial products added to fluffpulps during sheet forming which make the pulp sheet softer and easierto fluff. Debonders are closely related to fabric softeners chemically,and act in the same fashion. The force with which pulp fibers bond ismeasured indirectly by measuring the force (or energy) expended todebond or fluff a given pulp sheet.

[0031] The basis weight of a pulp sheet as described herein wasdetermined on some of the products presented in the examples using amethod based on TAPPI T220. A sheet of pulp, commonly 30 cm×30 cm or ofanother convenient dimension, was weighed and then dried to determinethe solids content (%) O.D.). The area of the sheet was then determinedand the ratio of O.D. (oven dried) weight to a defined area was reportedas the basis weight.

[0032] The caliper and sheet density were determined on some of theproducts presented in the examples using a method based on TAPPI T220.Sheet calliper was determined on test specimens from the basis weighttest using a motor driven micrometer that met TAPPI T411 conditions.Sheet density was calculated as the ratio of basis weight to caliper.

[0033] Mullen strength and burst indexes were determined on some of theproducts presented in the examples using a method based on TAPPI T807. ATMI Monitor Burst 1000 was used to measure the hydrostatic pressurerequired to rupture (bursting strength) the pulp sheet when the pressurewas increased at a controlled constant rate through a rubber diaphragmto a circular area 30.5 mm diameter. Mullen strength is recorded as kPa(kilo Pascals) at rupture, while burst index is the ratio of burstingstrength to basis weight.

[0034] A Kamas Lab hammermill Model H01-C was used to defiberize some ofthe products presented in the examples. Strips of pulp sheets 5 cm widewere fed into the hammermill, using 900 rpm motor speed, 50% feederspeed, and an 8 mm screen. In some cases, the energy required todefiberize the pulp sheet was recorded, and reported as W hr/kg offluff, the energy of defiberization. Fluff was collected in a collectionvacuum bag for further testing.

[0035] An M/K Formation Tester was used to measure the formation of pulpsheets for some of the samples presented in the examples. The formationis an expression of sheet uniformity. The M/K Formation Tester consistsof a rotating glass drum containing a traveling light source. A pulpsheet is wrapped around the outer surface of the drum. The light frominside the drum shines through the sheet and strikes a detector outsidethe drum. During the test, the drum rotates while the internal lightsource and the external detector move together down the axial length ofthe drum. In this way, the amount of light which passes through thesheet is measured at several different locations. The variation in theamount of light which passes through the sheet from point to point onthe sheet is used as a measure of the formation (uniformity offormation) of the sheet.

[0036] Weighted average fiber length (WADL) and fiber coarseness werealso measured for some of the products presented in the examples using aKajaani FS-200 Fiber Analyzer.

[0037] Fiber Property Performance Tests

[0038] SCAN testing of fluff pulp properties was carried out on some ofthe products presented in the examples. This test uses SCAN/PFImethodology (SCAN-C 33:80) and test equipment to form a uniform fluffsample, and to measure its resiliency, fluid retention and rate ofabsorption. The fluff samples are conditioned for at least 2 hours understandard conditions (23±1° C. and 50%±2% relative humidity) prior totesting and are kept in the conditioning atmosphere throughout the test.

[0039] A cylindrical fluff sample (3.00±0.05 g and 5 cm diameter) isprepared using special equipment. The height of the cylinder under a 260g/1.3 kPa load is measured and reported as resiliency. The sample isplaced in contact with a water bath. The time required for the water tomigrate vertically up the cylinder to the top is reported as absorptiontime. The fluid retention or absorption capacity per gram of sample iscalculated by weighing the saturated fluff sample.

[0040] A fluff sample can also be subjected to simulated heat-agingartificially (105° C. for two hours) and tested by this method todetermine effects of aging on fluff absorbent properties.

[0041] Dry classification of fluff pulp was carried out on some of theproducts presented in the examples. This test is a measure of fluffquality and the defiberization process. A Johnson Manufacturing FluffFiberization Measuring Instrument, Model 9010, was used to separate thefluff into three fractions based on particle size. During the test,fluff is pneumatically agitated to separate the fibers from each otherand from the undefibered pulpsheet. A vacuum draws the initial fines andthen the long fibers through a rotating sieve screen (16 mesh, 1.18 mmopening, U.S.A. std. series). The initial fines also pass through asecond screen, and accumulate in a dust bag. The long fibers (accepts)accumulate on a second screen (45 mesh, 0.36 mm opening, U.S.A. std.series).

[0042] Pad integrity testing was carried out on some of the productspresented in the examples. Pad integrity is a measure of the strength ofthe fiber network in fluffed pulps, and indicates how well the fluffwill maintain pad integrity in a dry formed absorbent product. Themethod is based on PFI method of 1981, “Measurement of Network Strengthin Dry, Fluffed Pulps”. During the test, a cylindrical test pad of1.0±0.05 gram and 50 mm diameter is prepared in a pad former. The testpad is placed in a burst chamber, which is then installed in astress-strain apparatus. A burst-body is vertically forced through thetest pad. The force required to rupture the fiber network in the testpad is reported as pad integrity.

[0043] The potential of a fibrous pulp for use as an acquisition layercan be described, among other tests, by a multiple “insult” or rewettingtest. The Multiple Insult—Absorption Testing procedure was carried outas follows. Pulps for comparison purposes are fiberized, thenairfiltered into pads with a basis weight of about 200 g/m². The padsare pressed at 200 psig for a period of two minutes then trimmed about 7cm×16 cm. The trimmed and densified pads are placed on top of a standardabsorbent core, such as a disposable diaper, and covered by a singlelayer of conventional polypropylene coverstock. Fluid is introduced tothe absorbent product through a cylinder permanently mounted to aweighted plate which applies a force of 0.1 psig to the absorbentproduct. A dam is used to control fluid flow to the absorbent product. Atimer is started when the dam is removed and fluid begins to move intothe absorbent product. The timer stops when all the fluid has beenabsorbed and the elapsed time recorded. Ninety seconds after the fluidis completely absorbed a stack of five preweighed blotter papers isplaced on top and then a 1.0 psig load is applied to the absorbentproduct for a period of two minutes. The amount of fluid wetted backinto the blotter paper is recorded. The procedure is repeated two timesfor a total of three wettings or “insults”. The multiple “insult” testcharacterizes the readiness with which fibers absorb as well asreabsorbs a fluid.

DETAILED DESCRIPTION OF THE INVENTION AND EMBODIMENTS THEREOF

[0044] As mentioned above, it has now been found that various pulps ofdiverse wood species prepared by diverse pulping and bleaching processesprovide improvements in these pulps by displaying improved fiber andpulp sheet properties, e.g. absorbency results such as for anacquisition layer in baby diapers, etc. upon cold alkali extraction(CAE) or cold caustic extraction (CCE) of these pulps in the propermanner in the proper sequence when preparing these pulps, i.e., whentreating the pulps. Relatively high strengths of sodium hydroxidesolution are used ideally, 13%-18% NaOH by weight for high absorbency,fast intensive absorbency applications and 5% to 15% for generalabsorbency application, preferably 6% to 100, for that purpose. By “coldcaustic extraction” (CCE) is meant the treatment of pulp at atemperature less than 60° C., preferably less than about 35° C., withthe above sodium hydroxide solutions. The process coextensive with thepreparation of the novel pulps is being claimed as an improvement forthe regime of the novel properties heretofore unrecognized in the art.The improvement thus also resides in a method for improving e.g. theabsorbency of the pulp, increasing the stiffness of fibers and otherproperties further described herein not heretofore known or recognized.

[0045] Moreover, it has been found as an embodiment that the appropriateacquisition layers absorbency performance can be established afteradequate bleaching of high K number unbleached pulp has been carried outto obtain aesthetically acceptable brightness values for the pulps withslightly lower cold caustic treatment (e.g. 15% NaOH versus 18% NaOH forunbleached pulps). At the lower concentration of cold caustic solutionpulps are obtained which are nearly as good as pulps obtained from CCEof the high K number unbleached pulps themselves.

[0046] Accordingly, it has been found that a specific desirable pulpproduct regime exists based on the process employed and the selection ofvarious product or fiber criteria as will be further described herein.For example, the absorbency relationships make the pulps in thecharacterized pulp product regime especially useful because the pulpsand their use can now be readily delineated from the regime ofunattractive uses and pulps not possessing the attractivecharacteristics. Moreover, the relationships within this novel regime ofother desirable properties has been established so as to delineate withgreat precision the claimed regime of the novel properties and thetechnique and process coextensive therewith.

[0047] Still further, while cold caustic treatment has been known forhigh quality dissolving pulps as discussed above, e.g. to make alphacellulose and some industrial product pulps, such treatment ascorrelated to the fiber and pulp sheet property variables listed aboveis novel with respect to pulps useful such as for absorbent pulps e.g.for an acquisition layer for products inter alia diapers, incontinentand catamenial devices, etc. including absorbent core materials forthese.

[0048] Added and further benefits will appear from the followingexamples and the illustrative embodiments. The examples are merely forthe purpose of illustration and are not intended to limit the scope ofthe invention.

EXAMPLE 1 Improved Pulp Sheet Defiberization: Debonders vs. Cold AlkaliExtraction, Kraft Southern Pine Pulp

[0049] Cellulosic pulp is commonly manufactured for fluff and otherfibrous end-use in dried, sheeted form. The pulp manufacturer operatesthe pulp machine to form the sheet from an aqueous suspension of fibers;the sheet once formed is dried to remove about 90% of the moisture.Large rolls of dried, sheeted pulp are produced off the dry end of thepulp machine. These are typically cut into smaller size rolls and/orbales of sheets for distribution to end-use customers.

[0050] It is an advantage that the dried, sheeted pulp defiber easilyand uniformly without damage to the individual fibers for those pulpgrades being used in various fibrous end-use applications. For example,a fluff pulp will be converted by the end-user from the dried, sheetedpulp to a pad of “fluffed” fibers by mechanical action such as issupplied by a Hammermill or other attrition mill. Chemical agents,debonders, are sometimes added to the pulp during sheet formation toinhibit interfiber bonding, which results in softer, more easilydefibered sheets. EXAMPLE 1, TABLE I-1 SAMPLE DESIGNATION A-1i B-1iSAMPLE DESCRIPTION Processing Non-debonded Debonded Standard ProcessStandard Process Wood Species Southern pine blend--------------->Pulping Process Kraft----------------------------> Sheet Debonder Used(?) No Yes COLD ALKALI Not Used Not Used EXTRACTION PULP ANALYTICAL 88.589.4 PROPERTIES ISO Brightness, % SHEET PHYSICS Basis Wt. (g/m²) 640 634Caliper (mm) 1.36 1.36 Density (g/cm³) 0.47 0.47 Mullen (kPa) 1113 417Burst Index (kPa · m²/g) 1.74 0.66 KAMAS FLUFF CHARACTERISTICSResiliency (cm) 4.1 3.7 Fluid Retention (g/g) 13.4 11.4 Absorption Time(s) Control 3.5 7.9 Heat-Aged 4.4 8.9 Dry Classification (wt. %) Accepts84.4 91.0 Knots 13.3 6.8 Fines 2.4 2.2 Pad Integrity (N) 7.2 7.0 EXAMPLE1, TABLE II-1 SAMPLE DESIGNATION A-1ii B-1ii SAMPLE DESCRIPTIONProcessing Standard Process Cold Alkali Extra- (Non-debonded) ctionProcess Wood Species Southern pine blend--------------> Pulping ProcessKraft---------------------------> Sheet Debonder Used (?) No No COLDALKALI Not Used Used EXTRACTION Alkali Used NaOH Solution Strength, %7.5 Temperature, ° C. 35 Time, H:M 10 Consistency, % 3 PULP ANALYTICAL88.6 89.6 PROPERTIES ISO Brightness, % SHEET PHYSICS Basis Wt. (g/m²)644 666 Caliper (mm) 1.12 1.17 Density (g/cm³) 0.57 0.57 Mullen (kPa)1494 829 Burst Index (kPa · m²/g) 2.32 1.25 KAMAS FLUFF CHARACTERISTICSResiliency (cm) 4.1 3.6 Fluid Retention (g/g) 12.9 13.2 Absorption Time(s) Control 3.3 2.9 Heat-Aged 4.9 4.6 Dry Classification (wt. %) Accepts81.2 91.4 Knots 15.9 6.0 Fines 2.9 2.7 Pad Integrity (N) 7.2 7.4 EXAMPLE1, TABLE III-1 SAMPLE DESIGNATION A-1iii B-1iii C-1iii SAMPLEDESCRIPTION Processing Non-debonded Debonded Cold Alkali StandardStandard Extraction Process Process Process Wood Species Southern pineblend---------------> Pulping Process Kraft---------------------------->Sheet Debonder Used (?) No Yes No COLD ALKALI Not Used Not Used UsedEXTRACTION Alkali Used NaOH Solution Strength, % 8.5 Temperature, ° C.35 Time, H:M 0:10 Consistency, % 3 PULP ANALYTICAL 86.6 88.4 88.9PROPERTIES ISO Brightness, % SHEET PHYSICS Basis Wt. (g/m²) 642 639 652Caliper (mm) 1.36 1.30 1.33 Density (g/cm³) 0.48 0.49 0.49 Mullen (kPa)1126 716 770 Burst Index (kPa · m²/g) 1.75 1.12 1.18 KAMAS FLUFFCHARACTERISTICS Resiliency (cm) 4.1 3.9 3.6 Fluid Retention (g/g) 13.512.4 12.5 Absorption Time (s) Control 3.3 7.1 2.5 Heat-Aged 4.3 7.7 3.0Dry Classification (wt. %) Accepts 84.2 87.4 94.6 Knots 13.1 10.3 3.6Fines 2.7 2.3 1.8

[0051] Table I-1 of Example 1 compares some of conventionally preparedsheet property and fluff characteristics of “non-debonded” bleachedkraft Southern pine pulp (Sample A-1i) to debonded (with chemicaldebonder added) bleached kraft Southern pine pulp (Sample B-1i. The pulpsheet products were produced on a commercial pulp machine. The sheetproperties (or sheet physics) as well as characteristics of the fluffedfiber were tested as produced by a small scale hammermill. The datagiven are averages of several tests on pulp from several productionruns. A description of the terms and tests has been given above.

[0052] In comparison to the standard process non-debonded, sheeted pulp,the standard process debonded sheeted pulp is softer (weaker) indicatedby the substantially lower pulp sheet Mullen strength as well as by thelower burst index. Note that the characteristics of the fluff from thedebonded pulp are poorer as indicated by the lower resiliency, lowerfluid retention, and increased (slower) absorption times compared tothose of the standard pulp fluff. The dry classification data of thefluffed fibers from the debonded pulp do indicate, however, that betteror more uniform defiberization was achieved (higher accepts, lowerknots). The fluff pad integrity was equivalent for both types of pulp.

[0053] In Table II-1 of Example 1, pulp produced by the process of thisinvention, cold alkali extraction (Sample B-1ii) is compared to standardprocess pulp (Sample A-1ii). Both types of pulp were pulped by the kraftprocess from a Southern pine chip furnish and were bleached to similarbrightness using standard chemicals/conditions of chlorine, chlorinedioxide, sodium hydroxide and sodium hypochlorite. The data given aremean data for several samples tested during standard production andtrial production periods. The conditions used during the cold alkaliextraction averaged about 7.5% NaOH solution strength, at about 35° C.for about 10 minutes at a pulp consistency of about 3%.

[0054] Note that the cold alkali extraction processed pulp sheet wassofter (about 45% lower in Mullen strength and in burst index) comparedto the standard process pulp sheet. Also, the dry classification data ofthe fluff produced upon small scale fluffing showed improvements in thegreater percent accepts and in the percent lower “knots” which indicatesimproved defiberability relative to the standard process pulp sheet. Inthese respects, the effect of the cold alkali extraction process on thepulp and fluff properties relative to the standard, non-debonded pulpwere similar to the effects of the use of a chemical pulp sheet debonderrelative to standard process pulp (Table I-1, Example 1) and, in fact,the novel pulps showed improved absorption properties. However, the coldalkali extraction process did not result in any negative consequences onfluff absorption times as does the use of a debonder. The fluidretention of the fluff from the cold alkali extraction processed pulpwas equivalent to that of the standard pulp (Table II-1, Samples A-1iiand B-1ii).

[0055] Note that the percentage improvement was greater in the weightpercent accepts (and in lower knot content) in the fluff from the coldalkali extraction process pulp compared to the fluff from standard pulp(Table II-1) than the comparable improvement associated with the use ofa sheet debonder (Table II-1). The dry classification accepts were 12%greater and the knots 62% reduced for the cold alkali extraction processpulp relative to its control standard process pulp, whereas accepts forthe debonded pulp were increased by only 8% with knot content reducedonly 49% relative to its standard process control pulp. Also, theserelative improvements were achieved by the cold alkali extractionprocessed pulp from a sheet that was actually somewhat harder than thedebonded pulp sheet (829 Mullen strength/1.25 burst index vs. 417 Mullenstrength/0.66 burst index).

[0056] The data presented in Table III-1, of Example 1 compare millproduction of both debonded and non-debonded standard pulps with trialproduction of cold alkali extraction pulp. All pulp types (SamplesA-1iii, B-1iii, and C-1iii) were produced from a Southern pine chipblend furnish by the kraft pulping process. All pulp types were bleachedwith chlorine dioxide, sodium hydroxide, oxygen and/or hydrogen peroxideto the brightness level indicated. The cold alkali extraction conditionsachieved averaged about 8.5% NaOH solution strength, at about 35° C. forabout 10 minutes applied to a pulp slurry at 3% consistency. About 0.2%H₂O₂ (O.D.—coven dried—pulp basis) had been added during the cold alkaliextraction.

[0057] Note that the debonded pulp and the cold alkali extracted pulpsheet were produced at approximately the same Mullen strength and burstindex, with both of these indicators of sheet hardness beingsubstantially reduced for either type of treated pulp, debonded or coldalkali extracted relative to the standard process control. Again, thefluff properties for the cold alkali extracted pulp showed somesimilarities to the debonded standard process pulp: resiliency and fluidretention were directionally lower for both relative to the standardpulp fluff. But the absorption times for fluff from the cold alkaliextracted pulp were better (faster) than for fluff from the debondedpulp or the standard process pulp. Fluff dry classification weightpercentage accepts and percentage knots were better for fluff from thetrial cold alkali extraction pulp.

[0058] Thus, the use of cold alkali extraction resulted in advantagesnot found with the standard process pulp and/or not expected from knowntechnology of applying sheet debonders to standard process pulp as ameans of “softening” the pulp sheet.

EXAMPLE 2 Cold Alkali Extraction for Fiber Property Improvement,Prehydrolyzed Kraft Southern Pine Pulp

[0059] The data presented in Tables I-2 and II-2 of Example 2 illustratethe pulp sheet and fiber property improvements which occurred when coldalkali extraction was applied to pulps cooked from a Southern pinefurnish by a prehydrolyzed kraft process. The prehydrolyzed kraftprocess is a two-stage pulping process, in which the raw materialfurnish is treated first under a mildly acidic condition (pH of about3-4), followed by an alkaline stage which is basically the kraft cookillustrated in Example 1. EXAMPLE 2, TABLE I-2 SAMPLE DESIGNATION A-2iB-2i SAMPLE DESCRIPTION Processing Non-debonded Cold Alkali StandardProcess Extraction Process Wood Species Southern pineblend-------------> Pulping Process Prehydrolyzed kraft------------>Sheet Debonded Used (?) No No COLD ALKALI EXTRACTION Not Used UsedAlkali Used NaOH Solution Strength, % 15 Temperature, ° C. 25 Time, H:M0:10 Consistency, % 3 PULP ANALYTICAL 89.4 86.7 PROPERTIES ISOBrightness, % SHEET PHYSICS Basis Wt. (g/m²) 652 818 Caliper (mm) 1.321.28 Density (g/cm³) 0.50 0.64 Mullen (kPa) 1154 716 Burst Index (kPa ·m²/g) 1.77 0.88 KAMAS FLUFF CHARACTERISTICS Resiliency (cm) 3.8 4.0Fluid Retention (g/g) 13.2 13.1 Absorption Time (s) Control 3.4 3.4Heat-Aged 4.2 6.1 Dry Classification (wt. %) Accepts 95.0 97.3 Knots 1.80.7 Fines 3.2 2.0 Pad Integrity (N) 6.8 7.3 MULTIPLE INSULT ABSORPTIONTEST Absorption times, seconds 1st insult 4.3 3.1 2nd insult 30.6 23.13rd insult 45.1 31.1 EXAMPLE 2, TABLE II-2 SAMPLE DESIGNATION A-2iiB-2ii SAMPLE DESCRIPTION Processing Non-debonded Cold Alkali StandardProcess Extraction Process Wood Species Southern pine blend------------>Pulping Process Prehydrolyzed kraft------------> Sheet Debonded Used (?)No No COLD ALKALI EXTRACTION Not Used Used Alkali Used NaOH SolutionStrength, % 10 Temperature, ° C. 25 Time, H:M 0:10 Consistency, % 3 PULPANALYTICAL 90.5 87.2 PROPERTIES ISO Brightness, % SHEET PHYSICS BasisWt. (g/m²) 847 897 Caliper (mm) 1.05 1.16 Density (g/cm³) 0.81 0.77Mullen (kPa) 1090 671 Burst Index (kPa · m²/g) 1.29 0.75 Kamas Energy(wh/kg) 116 83 KAMAS FLUFF CHARACTERISTICS Resiliency (cm) 3.8 3.7 FluidRetention (g/g) 14.1 13.9 Absorption Time (s) Control 4.2 3.8 Heat-Aged5.6 5.1 Dry Classification (wt. %) Accepts 95.3 95.4 Knots 1.1 1.4 Fines3.6 3.2 Pad Integrity (N) 8.1 6.1

[0060] Sample A-2i in Table I-2 is a prehydrolyzed kraft Southern pinepulp bleached with the conventional bleaching agents of chlorine,chlorine dioxide, hypochlorite and/or hydrogen peroxide and/or oxygenand sodium hydroxide to the ISO Brightness level indicated. Sample B-2iin Table I-2 is a similarly prehydrolyzed kraft pulp, similarly bleachedto the brightness indicated prior to cold alkali extraction.

[0061] The B-2i sample's processing included the cold alkali extractionprocess under the conditions listed (average conditions used). Both theA-2i and B-2i samples were produced in a mill scale facility duringproduction and trial runs, respectively.

[0062] As for the bleached Southern pine kraft pulp discussed in Example1, the use of cold alkali extraction resulted in a softer pulp sheet(i.e., of lower Mullen strength and lower burst index). Note that thehigher basis weight and density at which the B-2i sample pulp wasproduced should have had a negative impact on these sheet properties. Inaddition, the resiliency and fluid retention of the cold alkaliextracted Sample B-2i were equivalent to those of Sample A-2i and thedry fluff classification results showed some improvement for SampleB-2i. Kamas fluff absorption times were similar (slightly longer forSample B-2i upon heat-aging), but the specialized multiple insultabsorption tests (described above) showed that cold alkali extractionimproved the absorption properties of the resulting fiber.

[0063] The data presented in Table II-2 also compare bleachedprehydrolyzed kraft Southern pine pulps (pulping conditions were moresevere than those used for the samples in Table I-2 of this example).

[0064] Sample A-2ii was produced without, Sample B-2ii with cold alkaliextraction. Both types were also produced in a mill-scale facility andused common bleaching techniques to reach the brightness levelsindicated. The sodium hydroxide solution strength used was lower thanthat used for the samples described in Table I-2 of this example, 10%vs. 15%.

[0065] Comparison of sheet property data again shows the sheet softeningeffects resulting from the use of cold alkali extraction: lower Mullenstrength, lower burst index. Also, a Kamas energy parameter (seedescription above) was recorded to describe the relative ease ofdefibering the pulp sheet during the fluffing operation in thelaboratory. The cold alkali extracted pulp was fluffed more easily (withless energy input). Fluff absorptions were slightly faster for the coldcaustic extracted Sample B-2ii. Dry classification of the fluffed fiberswere equivalent for both samples as were resiliency and fluid retention.However, fluff pad integrity (see description above) was poorer for thecold caustic extracted Sample B (this was not the case with Sample B-2iicompared to Sample A-2i in Table I-2 of this example).

EXAMPLE 3 Cold Alkali Extraction Process: Variable Solution Strength

[0066] From the data given in Tables I-3 through VI-3 of this example,it is apparent that no one set of cold alkali extraction processconditions will result in exactly the same consequences on every type ofpulp. Raw material/furnish used, pulping process used, and the positionof cold alkali extraction within a bleaching sequence have consequenceson what may be the optimum conditions for each type of sample. Secondly,it appears that cold alkali extraction conditions can be selected toenhance some of the fiber properties of the resulting pulp but at theexpense of others. Not all fibrous end-uses require improvements in thesame properties, thus this apparent versatility of cold alkaliextraction conditions might be used to tailor pulp fibers for variousfibrous end-use products and/or customers. These points will bediscussed in this and subsequent examples. EXAMPLE 3, TABLE I-3 SAMPLEDESIGNATION A-3i B-3i C-3i SAMPLE DESCRIPTION Processing Non-debondedCold Alkali Standard process Extraction Process----> Wood SpeciesSouthern pine blend-----------------> Pulping ProcessKraft-------------------------------> K Number, mL18----------------------------------> COLD ALKALI Not UsedUsed---------------> EXTRACTION Alkali Used (Control) NaOH NaOH SolutionStrength, % 7 12 Temperature, ° C. 35 35 Time, H:M 0:15 0:15Consistency, % 3 3 PULP ANALYTICAL 83.3 92.2 91.4 PROPERTIES ISOBrightness, % SHEET PHYSICS Basis Wt. (g/m²) 725 737 691 Caliper (mm)1.75 2.14 2.41 Density (g/cm³) 0.41 0.35 0.29 Mullen (kPa) 1179 527 70Burst Index (kPa · m²/g) 1.63 0.72 0.10 KAMAS FLUFF CHARACTERISTICSResiliency (cm) 3.8 3.9 3.7 Fluid Retention (g/g) 13.3 12.2 14.6Absorption Time (s) Control 3.7 2.9 3.9 Heat-Aged 4.3 3.6 4.1 DryClassification (wt. %) Accepts 97.5 98.5 89.0 Knots 1.2 0.1 8.6 Fines1.3 1.4 2.4 Pad Integrity (N) 6.7 6.4 5.3

[0067] EXAMPLE 3, TABLE II-3 SAMPLE DESIGNATION A-3ii B-3ii C-3ii D-3iiE-3ii SAMPLE DESCRIPTION Processing Non-debonded Cold Alkali ExtractionProcess→ Standard Process Wood Species Southern pine blend→ → → → →Pulping Process Kraft→ → → → → K Number, mL 18→ → → → → COLD ALKALIEXTRACTION Alkali Used None (water) NaOH→ → → → Solution Strength, % 0 37 14 Temperature, ° C. 35→ → → → → Time, H:M 0:10→ → → → → Consistency,% 3→ → → → → PULP ANALYTICAL PROPERTIES 87.9 90.3 92.1 92.0 ISOBrightness, % SHEET PHYSICS Basis Wt. (g/m²) 711 677 676 691 Caliper(mm) 1.87 2.03 2.06 2.79 Density (g/cm³) 0.38 0.34 0.33 0.26 Mullen(kPa) 1189 1005 501 83 Burst Index (kPa · m²/g) 1.67 1.48 0.75 0.12Kamas Energy (wh/kg) 109.5 99 92.7 — KAMAS FLUFF CHARACTERISTICSResiliency (cm) 3.8 3.5 3.3 3.3 Fluid Retention (g/g) 11.8 11.3 11.213.2 Absorption Time (s) 4.1 2.8 2.6 4.0 Control Dry Classification (wt.%) Accepts 94.6 94.3 94.0 75.9 Knots 2.0 2.7 3.2 21.1 Fines 3.4 3.0 2.83.1 Pad Integrity (N) 7.4 6.4 5.7 4.2 SAMPLE DESCRIPTION Processing ColdAlkali Extraction Process→ → → → Wood Species Southern pine blend→ → → →→ Pulping Process Prehydrolyzed kraft→ → → → → K Number, mL 18→ → → → →COLD ALKALI EXTRACTION Alkali Used Sodium hydroxide (NaOH)→ → → → →Solution Strength, % 7.0 11.0 13.1 15.1 18.2 Temperature, ° C. 35° C.→ →→ → → Time, H:M 0:15→ → → → → Consistency, % 3→ → → → → PULP ANALYTICALPROPERTIES 88.0 88.3 85.3 85.3 85.7 ISO Brightness, % MULTIPLE INSULTABSORPTION TESTS Absorption Times, seconds 1st insult 7.6 6.6 6.8 6.26.5 2nd insult 37.6 26.2 25.1 21.8 22.4 3rd insult 58.6 44.9 36.5 35.033.0

[0068] EXAMPLE 3, TABLE IV-3 SAMPLE DESIGNATION A-3iv B-3iv C-3iv D-3ivE-3iv F-3iv SAMPLE DESCRIPTION Processing Unbleached Pulp UnbleachedPulp Before Cold Alkali After Cold Alkali Extraction Extraction→ → → →Wood Species Southern pine blend→ → → → → → Pulping Process Kraft→ → → →→ → K Number, mL 8.2→ → → → → → COLD ALKALI EXTRACTION Not Used Used→ →→ → → Alkali Used (Control) NaOH→ → → → → Solution Strength, % 6 9 12 1518 Temperature, ° C. 30° C.→ → → → → Time, H:M 0:15→ → → → →Consistency, % 3.0→ → → → → MULTIPLE INSULT ABSORPTION TEST Absorptiontimes, seconds 1st insult 8.9 8.2 6.7 7.5 7.4 8.3 2nd insult 43.8 43.730.7 32.8 29.6 31.7 3rd insult 64.5 88.5 51.2 48.3 50.0 48.3

[0069] EXAMPLE 3, TABLE V-3 SAMPLE DESIGNATION A-3v B-3v SAMPLEDESCRIPTION Processing Standard Process Cold Alkali (Non-debonded)Extraction Wood Species Southern pine blend→ → K Number, mL 12.4→ → COLDALKALI EXTRACTION Not Used Used Alkali Used (Control) NaOH SolutionStrength 6 Temperature, ° C. 28 Time, H:M 0:15 Consistency, % 3 PULPANALYTICAL PROPERTIES 84.8 84.8 ISO Brightness, % SHEET PHYSICS BasisWt. (g/m²) 644 599 Caliper (mm) 1.33 1.40 Density (g/cm³) 0.53 0.44Mullen (kPa) 1656 834 Burst Index (kP · m²/g) 2.63 1.44 Kamas Energy(wh/kg) 69.5 47.9 KAMAS FLUFF CHARACTERISTICS Resiliency (cm) 4.1 3.7Fluid Retention (g/g) 12.0 11.8 Absorption Time (s) Control 3.2 2.9Heat-Aged 4.8 4.5 Dry Classification (wt. %) Accepts 86.6 88.7 Knots11.8 9.3 Fines 1.6 1.9 Pad Integrity (N) 7.1 7.0 SAMPLE DESIGNATIONA-3vi B-3vi C-3vi D-3vi E-3vi SAMPLE DESCRIPTION Processing StandardCold Alkali Extraction Process→ → Process (non- debonded) Wood SpeciesSouthern hardwood blend→ → → → → Pulping Process Kraft→ → → → → KNumber, mL 11.0→ → → → → COLD ALKALI EXTRACTION Alkali Used None Sodiumhydroxide→ → → (control) Solution Strength, % — 9 12 15 18 Temperature,° C. 30° C.→ → → → → Time, H:M 0:15→ → → → → Consistency, % 3→ → → → →PULP ANALYTICAL PROPERTIES 31.5 43.2 38.6 37.6 37.8 ISO Brightness, %KAMAS FLUFF CHARACTERISTICS Resiliency (cm) 3.4 2.9 2.9 3.0 2.7 FluidRetention (g/g) 12.5 12.2 13.0 13.2 12.6 Adsorption Time (s) Control 6.24.5 4.0 4.3 3.8 Heat-Aged 12.9 8.1 9.3 7.1 6.5 Dry Classification (wt.%) Accepts 93.2 93.7 91.6 91.5 90.4 Knots 0.7 0.6 0.6 0.7 0.5 Fines 6.15.7 7.6 7.8 9.1 Pad Integrity (N) 3.6 4.4 4.1 4.3 4.1 MULTIPLE INSULTABSORPTION TEST Absorption times, seconds 1st Insult 13.3 11.9 11.4 11.710.7 2nd Insult 55.3 46.1 46.8 45.8 45.9 3rd Insult 98.5 64.2 67.3 73.674.3

[0070] EXAMPLE 3, TABLE VI-3 SAMPLE DESIGNATION A-3vi B-3vi C-3vi D-3viE-3vi SAMPLE DESCRIPTION Processing Standard Cold Alkali ExtractionProcess→ Process (non- debonded) Wood Species Southern hardwood blend→ →→ → Pulping Process Kraft→ → → → → K Number, mL 11.0→ → → → → COLDALKALI EXTRACTION Alkali Used None Sodium hydroxide→ → → (control)Solution Strength, % — 9 12 15 18 Temperature, ° C. 30° C.→ → → → →Time, H:M 0:15→ → → → → Consistency, % 3→ → → → → PULP ANALYTICALPROPERTIES 31.5 43.2 38.6 37.6 37.8 ISO Brightness, % KAMAS FLUFFCHARACTERISTICS Resiliency (cm) 3.4 2.9 2.9 3.0 2.7 Fluid Retention(g/g) 12.5 12.2 13.0 13.2 12.6 Adsorption Time (s) Control 6.2 4.5 4.04.3 3.8 Heat-Aged 12.9 8.1 9.3 7.1 6.5 Dry Classification (wt. %)Accepts 93.2 93.7 91.6 91.5 90.4 Knots 0.7 0.6 0.6 0.7 0.5 Fines 6.1 5.77.6 7.8 9.1 Pad Integrity (N) 3.6 4.4 4.1 4.3 4.1 MULTIPLE INSULTABSORPTION TEST Absorption times, seconds 1st Insult 13.3 11.9 11.4 11.710.7 2nd Insult 55.3 46.1 46.8 45.8 45.9 3rd Insult 98.5 64.2 67.3 73.674.3

[0071] The data given in Table I-3 of this example cover laboratoryexperiments on bleached Southern pine kraft pulp. All Samples A-3ithrough C-3i were bleached to the brightness indicated with the commonbleaching chemicals of chlorine dioxide, hydrogen peroxide and sodiumhydroxide. The cold alkali extracted Sample B-3i and C-3i wereadditionally bleached with chlorine dioxide subsequent to cold alkaliextraction (this contributed to the higher brightness levels of SamplesB-3i and C3i . The NaOH solution strength used in the cold alkaliextraction of Sample B-3i was relatively low (7% compared to that usedfor Sample C-3i, 12%). These samples were sheeted (non-directional sheeton a laboratory sheet mold) and dried under the same standard conditionsin the laboratory (but dried without restraint unlike a commercial pulpmachine) so that the changes in pulp sheet and fiber/fluff propertiesmeasured reflect the cold alkali extraction process alone. Thus forSample B-3i, cold alkali extraction resulted in fibers which formed asheet which was fluffed into fibers with the following propertiesrelative to Sample A-3i (non-cold caustic extraction): similar basisweight, higher caliper, lower density, lower Mullen strength and lowerburst index; equivalent fluff resiliency but reduced fluid retention,faster absorption times and somewhat improved dry fluff classificationprofiles. For Sample C-3i (cold caustic extracted at 12% NaOH solutionstrength) relative to Sample A-3i (non-cold caustic extracted) thecomparison/contrast was as follows: slightly reduced basis weight,higher caliper, lower density, much lower Mullen strength and burstindex (very weak sheet); equivalent fluff resiliency, higher fluffretention, similar Kamas fluff absorption times, and poorer dry fluidclassification profile. Thus, if an end-use required a fiber of highestfluid retention, a higher caustic solution strength could be selected;to maximize accept fiber upon fluffing, a lower caustic strength wouldbe preferable.

[0072] In Table II-3 of this Example 3, data are presented as additionaldata on bleached Southern pine kraft pulp, produced in the laboratoryover a wider range of cold alkali extraction solution strengths. Allsamples A-3ii through D-3ii were bleached with the common bleachingagents of chlorine, chlorine dioxide, hydrogen peroxide and oxygen(prior to cold alkali extraction) to the ISO brightness levelsindicated. Even at 3% NaOH solution strength, the pulp sheet can besomewhat softened without any large negative consequences on fluffproducts. However, cold caustic extraction at 14% NaOH solution strengthappear to result in a pulp sheet that was fluffed with apparent negativeconsequences on dry classification and resiliency with no advantage inabsorption time but with a slightly higher fluid retention.

[0073] Results from a similar series of bleached prehydrolyzed kraftSouthern pine pulps cold caustic extracted over a range of from 7 to 18%NaOH solution strength are presented in Table III-3. All samples A-3iiithrough E-3iii were bleached with chlorine, chlorine dioxide, sodiumhypochlorite and sodium hydroxide prior to cold caustic extraction. Themultiple insult absorption test results indicate that little benefitwould be gained by using NaOH solution strength in the cold causticextraction (under the temperature, time and consistency shown) greaterthan about 13% for this type of pulp, and that absorption times improve(decrease) progressively when using a 7% to 13% caustic solution.

[0074] Similarly, data are given in Table IV-3 of this example whichillustrate a levelling off of improvement of absorption times withincreasing cold alkali extraction solution strengths (6-18%). SamplesB-3iv through F-3iv were all cold alkali extracted from the startingmaterial Sample A-iv. No bleaching chemicals were used on any of theSamples A-3iv through F-3iv. Sample A3iv was a Southern pine pulp cookedto very, very low K Number via a single stage conventional kraft cook inthe laboratory. Multiple insult absorption times of-the fluff fiberswere improved with the use of a 9% NaOH solution strength with nofurther benefit being seen above the 9% strength. Thus a similar trendtoward a levelling off of absorption times with increasing solutionstrength seen from application of cold alkali extraction was observedfor this low K Number unbleached kraft Southern pine pulp as had beenobserved for the bleached prehydrolyzed kraft pulp sample series givenin Table III-3 of this example. But the level of the absorption times atwhich each type of pulp absorbed and the solution strength at which theabsorption time improved occurred differently with the type of pulpextracted.

[0075] For a very low K Number bleached kraft pulp, cold alkaliextraction at relatively low NaOH solution strength has many advantagesother than faster absorption times. Data are given in Table V-3 of thisexample which compare two samples (A-3v without and B-3v with) of pulppulped to 12.4 K Number and bleached to 84.8% ISO Brightness. The coldcaustic extraction conditions used for Sample B-3v were a relatively lowsolution strength of 6%, at 28° C. for 15 minutes at a pulp consistencyof 3%. This cold alkali extraction was used prior to bleaching to theindicated brightness. Both types of pulp samples (data averages givenfor A-3v and B-3v were bleached using chlorine dioxide, hydrogenperoxide and sodium hydroxide.

[0076] One of the largest drawbacks to pulping to low K Number by thekraft process is the negative consequences on fiber properties thatresult from the extensive pulping. Please compare the higher sheetMullen strength and burst index of Sample A-3v, Table V-3 to those ofthe samples in Tables I-3 and II-3 of this Example 3. When theprocessing used on the low K Number included cold alkali extraction(Sample B-3v, Table V-3), these disadvantages were overcome. Inaddition, the fluff characteristics of fibers from the B-3v sample low KNumber pulp were equivalent to or better than the A-3v low K Number pulpsample (Table V-3, similar fluid retention, somewhat faster Kamas fluffabsorption times and somewhat improved dry fluff classificationprofile).

[0077] In Table VI-3 of this example, data are presented for a series ofunbleached kraft pulp cooked from a Southeastern United States blend ofhardwoods (gums, oaks, etc.) to a low (11.0) K Number. Cold caustic NaOHsolution strength was varied from 9 to 18% for Samples B-3vi throughE-3vi; Sample A-3vi was the starting pulp prior to cold alkaliextraction. No bleaching chemicals were used on these samples. The 9%NaOH solution strength appears to be optimum of the conditions studiedfor this type of pulp in the unbleached state: Kamas fluff and multipleinsult absorption times are basically constant at 9% and higher solutionstrengths. Dry classification profile for the fluff deteriorate atsolution strengths at or above 12%. For this type of hardwood pulp, evenlower NaOH strength might prove to be more desirable. Note that hardwoodpulps do not match softwood pulps in these types of fibrous propertyperformance tests. However, cold alkali extraction can be used toimprove some of these fiber/fluff properties to some extent for bothtypes of furnishes.

EXAMPLE 4 Sulfite Pulps: Debonders; Cold Alkali Extraction

[0078] Debonders can be used on sulfite process pulps as well as onkraft pulps. Data are presented in Table I-4, Example 4 for commerciallyavailable sulfite pulps. The pulping process used is acid sulfite (alsoknown as acid bisulfite); both pulps are bleached to the brightnessindicated by common bleaching agents such as chlorine, chlorine dioxide,hydrogen peroxide and sodium hydroxide. Data given are averaged fromseveral tests of each type of production, non-debonded (A4i) anddebonded (B4i). EXAMPLE 4, TABLE I-4 SAMPLE DESIGNATION A-4i B-4i SAMPLEDESCRIPTION Processing Standard process Standard process non-debondeddebonded Wood Species Northwest U.S. softwood blend, predominantlyDouglas fir------------------------------------> Pulping ProcessSulfite----------------------------------------> Sheet Debonder Used (?)No Yes COLD ALKALI EXTRACTION Not Used Not Used PULP ANALYTICALPROPERTIES 91.8 91.2 ISO Brightness, % SHEET PHYSICS Basis Wt. (g/m²)698 684 Caliper (mm) 1.25 1.34 Density (g/cm³) 0.56 0.51 Mullen (kPa)479 279 Burst Index (kPa · m²/g) 0.69 0.41 Kamas Energy (wh/kg) 41.028.7 KAMAS FLUFF CHARACTERISTICS Resiliency (cm) 3.7 3.6 Fluid Retention(g/g) 13.2 12.1 Absorption Time (s) Control 11.8 6.3 Heat-Aged 43.6 6.0Dry Classification (wt. %) Accepts 77.9 87.5 Knots 16.0 7.1 Fines 6.15.4 Pad Integrity (N) 6.3 6.4 EXAMPLE 4, TABLE II-4 SAMPLE DESIGNATIONA-4ii B-4ii C-4ii D-4ii SAMPLE DESCRIPTION Processing Standard ProcessStandard Process Cold Alkali Cold Alkali (non-debonded) (non-debonded)Extraction Extraction Unbleached Bleached Process Process UnbleachedBleached Wood Species Southern pineblend-------------------------------> Pulping Process Acidsulfite---------------------------------------> K Number, mL 34 28 34 28COLD ALKALI EXTRACTION Not Used Not Used Used Used Alkali Used NaOH NaOHSolution Strength, % 15 15 Temperature, ° C. 30 30 Time, H:M 0:15 0:15Consistency, % 3 3 PULP ANALYTICAL PROPERTIES — 86 — 86 ISO Brightness,% MULTIPLE INSULT ABSORPTION TEST Absorption times, seconds 1st insult13.2 7.9 6.8 8.1 2nd insult 36.3 37.2 20.9 27.3 3rd insult 45.1 63.530.1 38.6 EXAMPLE 4, TABLE III-4 SAMPLE DESIGNATION A-4iii B-4iii SAMPLEDESCRIPTION Processing Standard Cold Alkali Processing Extraction(non-debonded) Process Wood Species Caribbeanpine-------------------------> Pulping ProcessSulfite--------------------------------> K Number24------------------------------------> COLD ALKALI EXTRACTION Not UsedUsed Alkali Used Not Used NaOH Solution Strength, % 15.4 Temperature, °C. 30 Time, H:M 0:37 Consistency, % 8 PULP ANALYTICAL PROPERTIES 77.5ISO Brightness, % KAMAS FLUFF CHARACTERISTICS Resiliency (cm) 3.4 2.9Fluid Retention (g/g) 12.1 13.0 Absorption Times (s) Control 2.8 3.5Heat-Aged 4.4 4.4 Dry Classification (wt. %) Accepts 92.4 80.4 Knots 1.611.3 Fines 6.0 8.3 MULTIPLE INSULT ABSORPTION TESTS Absorption Times,seconds 1st insult 38.1 15.9 2nd insult 88.2 45.0 3rd insult 135.8 69.6EXAMPLE 4, TABLE IV-4 SAMPLE DESIGNATION A-4iv B-4iv SAMPLE DESCRIPTIONProcessing Standard Cold Alkali Process Extraction (non-debonded) WoodSpecies Douglas fir-------------------------------------> PulpingProcess Sulfite---------------------------------------> K Number, mL26.6----------------------------------------> COLD ALKALI EXTRACTION NotUsed Used Alkali Used NaOH Solution Strength, % 15.4 Temperature, ° C.30 Time, H:M 1:00 Consistency, % 13 PULP ANALYTICAL PROPERTIES — 83.4ISO Brightness, % KAMAS FLUFF CHARACTERISTICS Resiliency (cm) 3.5 2.5Fluid Retention (g/g) 14.1 13.0 Absorption Time (s) Control 4.6 3.8Heat-Aged 6.2 4.5 Dry Classification (wt. %) Accepts 87.8 65.4 Knots 6.626.6 Fines 5.6 8.0 MULTIPLE INSULT ABSORPTION TEST Absorption times,seconds 1st insult 47.2 28.9 2nd insult 103.3 59.9 3rd insult 137.9 77.2

[0079] As in the Example 1, Table I-1, which illustrated the effects ofdebonders on bleached kraft pulp sheet properties, debonders can act to“soften” the softwood sulfite sheet. Note the lower Mullen strength,burst index and Kamas energy of Sample B-4i compared to Sample A4i.There is also a similar trend toward lower fluid retention for thedebonded pulp as was seen with the kraft pulp. The dry fluffclassification profile is improved toward greater accepts, lower knotsas was the case with the kraft pulp. However, sulfite pulps differ fromkraft pulps in that the use of debonders improve absorption times forsulfite pulps (related to the differences in wood derived extractives inacid sulfite pulps). Note the long fluff absorption times for thenon-debonded sulfite pulp.

[0080] However, for sulfite pulps the use of cold alkali extraction canhave additional advantages and can improve performance in the multipleinsult test. Data are given in Table II-4 of this example which comparemultiple insult tests for unbleached vs. bleached sulfite Southern pinepulps, processed with and without cold alkali extraction. Samples B4iiand D-4ii were bleached with common bleaching agents such as chlorine,chlorine dioxide,. hydrogen peroxide and sodium hydroxide. Samples A-4iiand C-4ii represent two high K Number unbleached Southern pine sulfitepulps. Sample C-4ii was cold alkali extracted using the conditionsindicated in Table II-4 from Sample A-4ii; Sample D-4ii was cold alkaliextracted from Sample B-4ii.

[0081] These data indicate that cold alkali extraction can minimizedifferences in multiple insult performance of these Southern pinesulfite pulps apparent for unbleached vs. bleached pulp. Please comparethe delta (Δ) for first absorption times for (A-4ii to B-4ii) of 5.3seconds, but for delta first absorption times for D-4ii to C-4ii) of 1.3seconds; delta for third absorption times for (B-4ii to A-4ii) of 18.4seconds, but only a delta of 8.5 seconds for the third absorption timesfor (D-4ii to C-4ii). Thus cold alkali extraction reduced the magnitudesof the differences in absorption times between unbleached and bleachedpulps as well as improving the actual level at which both cold causticextracted samples C and D performed (reduced all absorption times,further discussion of these samples is given in Example 5).

[0082] Data are presented in Tables III-4 and IV-4 of Example 4 forsulfite pulps which demonstrate the effects of using relatively highsodium hydroxide solution strengths for cold alkali extraction overlonger retention time and at higher consistency than were used in theprevious examples and tables. All four pulp samples (A-4iii and B-4iii,Table III, A4iv and B-4iv, Table IV) were bleached using the common pulpbleaching chemicals of chlorine dioxide, hydrogen peroxide and sodiumhydroxide. Acid sulfite pulping was used to cook a Caribbean pine chipfurnish to 24 K Number (Table III-4); acid sulfite pulping was used tocook Douglas fir to about 27 K Number (Table IV-4). When cold alkaliextraction was used (for the B samples of both these tables, i.e., B4iiiand B4iv), it followed an initial bleaching stage treatment of theunbleached pulp with chlorine dioxide. Bleaching was continued followingthe cold alkali extraction to the brightness level indicated usingchlorine dioxide, hydrogen peroxide and sodium hydroxide.

[0083] For the sulfite Caribbean pine pulp, the use of cold alkaliextraction at 15.4% NaOH under the conditions listed resulted in fibersshowing significant improvement in the multiple insult absorption testtimes (all three insult times were reduced about 50%). Kamas fluffcharacteristics were similar for the B-4ii sample compared to the A-4iiisample with the exception of a poorer dry classification profile for thecold caustic extracted sample B-4iii . This may be due to in optimallyhigh NaOH solution strength for this type of pulp as was observed forsome types of kraft pulps discussed under Example 4, and/or the higherconsistency and/or longer time at which the relatively highconcentration was used could be non-optimum.

[0084] For the sulfite Douglas fir pulp of Table IV-4, the use of coldalkali extraction also markedly improved the multiple insult absorptiontest times; Kamas fluff absorption times were also faster but fluffresiliency and fluid retention appeared to be more greatly affected forCaribbean pine of Table III-4. The fluff dry classification profile wasalso poorer with cold alkali extraction of this Douglas fir sulfitepulp. Again, as with the sulfite Caribbean pine sample and with thekraft pulp examples discussed in Example 4, these cold alkali extractionconditions may be non-optimum for fiber properties other than absorptiontime improvement for this type of bleached sulfite softwood fiber.

EXAMPLE 5 Kraft and Sulfite Southern Pine Pulps

[0085] The following unbleached kraft pulp (Sample A-5i—Table I-5,Example 5) with a K Number of 30 was obtained from a Southern pine chipfurnish. This pulp was prepared by a routine conventional kraft pulpingprocess using methodology common to the industry. A sulfate process wasused on a Southern pine chip furnish to characterize the behavior offibers pulped from the same species via different pulping processes.This pulp was prepared by an acid bisulfite process (sulfite process)common to the industry. This pulp (Sample A-5i—Table I-5, Example 5) hada K Number of 34. EXAMPLE 5, TABLE I-5 SAMPLE DESIGNATION A-5i B-5i C-5iSAMPLE DESCRIPTION Processing Unbleached Pulp Unbleached Pulp UnbleachedPulp Before Cold Alkali After Cold Alkali After Cold Alkali ExtractionExtraction Extraction Wood Species Southern pineblend---------------------------> Pulping ProcessKraft----------------------------------------> K Number, mL 30 — — COLDALKALI EXTRACTION Not Used Used Used Alkali Used NaOH NaOH SolutionStrength, % 15 18 Temperature, ° C. 30 30 Time, H:M 0:15 0:15Consistency, % 3.0 3.0 PULP ANALYTICAL PROPERTIES — — — ISO Brightness,% MULTIPLE INSULT ABSORPTION TEST Absorption times, seconds 1st insult9.5 5.6 5.3 2nd insult 36.3 20.2 18.7 3rd insult 56.9 32.4 26.7 EXAMPLE5, TABLE II-5 SAMPLE DESIGNATION A-5ii B-5ii C-5ii SAMPLE DESCRIPTIONProcessing Unbleached Pulp Pulp After Cold Pulp After Cold Before ColdAlkali Alkali Extraction Alkali Extraction Extraction Wood SpeciesSouthern pine blend----------------------------> Pulping ProcessSulfite----------------------------------------> K Number, mL 34 — —COLD ALKALI EXTRACTION Not Used Used Used Alkali Used NaOH NaOH SolutionStrength, % 15 18 Temperature, ° C. 30 30 Time, H:M 0:15 0:15Consistency, % 3.0 3.0 MULTIPLE INSULT ABSORPTION TEST Absorption times,seconds 1st insult 13.2 6.9 5.1 2nd insult 36.3 24.5 18.6 3rd insult45.1 32.3 23.2 EXAMPLE 5, TABLE III-5 SAMPLE DESIGNATION A-5iii B-5iiiC-5iii SAMPLE DESCRIPTION Processing Bleached Pulp Bleached PulpBleached Pulp Before Cold Alkali After Cold Alkali After Cold AlkaliExtraction Extraction Extraction Wood Species Southernpine-blend--------------------------> Pulping ProcessKraft---------------------------------------> COLD ALKALI EXTRACTION NotUsed Used Used Alkali Used NaOH NaOH Solution Strength, % 15 18Temperature, ° C. 30 30 Time, H:M 0:15 0:15 Consistency, % 3.0 3.0 PULPANALYTICAL PROPERTIES 92 — — ISO Brightness, % MULTIPLE INSULTABSORPTION TEST Absorption times, seconds 1st insult 8.9 5.5 6.4 2ndinsult 41.6 18.8 23.1 3rd insult 69.1 33.4 37.3

[0086] Despite the different pulping processes, the Southern pine chipfurnish yielded fibers having excellent absorption results after coldalkali extraction (Tables I-5 and II-5 or Example 5, the alkali usedbeing sodium hydroxide). Each of the unbleached pulps was treated with acold caustic solution of 15% and 18% NaOH (weight %). The cold causticextraction was carried out as follows. Pulps of 3% consistency [O.D.pulp weight/total weight (caustic solution+O.D. pulp)×100] were treatedat about 30° C. for about 15 minutes by stirring the suspension. Foreach different caustic solution treated sample, the absorbency wasdetermined and compared for the respective draft and sulfite pulp. It isnoted that extraction with 18% NaOH gave the best test results for eachof the pulp stocks.

[0087] For comparison, the unbleached kraft Southern pine pulp wasbleached to an ISO brightness of 92% prior to applying the cold alkaliextraction process (Sample A-5iii. Table III-5 Example 5). This pulp wasthe same pulp used as the starting material for bleaching in Example 5(Sample A-5i, Table I-5). However, prior to cold caustic extraction itwas bleached with the chemicals of chlorine, chlorine dioxide, hydrogenperoxide, oxygen and sodium hydroxide. The results obtained are shown inTable III-5 when following the same cold caustic extraction procedure asoutlined above.

[0088] From the comparison of the data in Tables I-5 and II-5 of thisexample, it is evident that for the unbleached pulp an increase inconcentration of the cold caustic solution to 18% NaOH improved theabsorption properties; for bleached pulp (Sample A-5iii, Table III-5)the higher concentration (i.e., 18% NaOH reduced the absorbencyproperties compared to extraction with 15% NaOH. However, note that theabsorbency properties of the bleached pulp cold caustic extracted with15% NaOH were distinctly better than those of the bleached pulpprocessed without any cold alkali extraction.

EXAMPLE 6 Prehydrolyzed Kraft Bleached Southern Pine Pulp

[0089] In a manner similar to that used for Example 5, the absorptionproperties were determined for a bleached, prehydrolyzed kraft pulp fromSouthern pine wood. This pulp was prepared by a routine prehydrolyzedkraft pulping process using methodology common to the industry and wasbleached using the chemicals of chlorine, chlorine dioxide, sodiumhydroxide, and sodium hypochlorite to an ISO Brightness of 86%. The KNumber of the unbleached pulp was about 18 mL. EXAMPLE 6, TABLE I-6SAMPLE DESIGNATION A-6i B-6i C-6i SAMPLE DESCRIPTION Processing BleachedPulp Bleached Pulp Bleached Pulp Before Cold Alkali After Cold AlkaliAfter Cold Alkali Extraction Extraction Extraction Wood Species Southernpine--------------------------------> Pulping Process Steamprehydrolyzed kraft---------------------> COLD ALKALI EXTRACTION NotUsed Used Used Alkali Used NaOH NaOH Solution Strength, % 15 18Temperature, ° C. 30 30 Time, H:M 0:15 0:15 Consistency, % 3.0 3.0 PULPANALYTICAL PROPERTIES 86 — — ISO Brightness, % MULTIPLE INSULTABSORPTION TEST Absorption times, seconds 1st insult 6.7 4.9 6.2 2ndinsult 46.6 19.6 25.5 3rd insult 77.2 32.3 41.9

[0090] The absorption results after cold alkali extracting this pulpwith 15% and 18% NaOH are shown in Table I-6, and confirm the effectcaused by CCE treatment on the absorbency of the pulp. Again, this pinepulp subjected to extraction after bleaching with 15% NaOH (Sample A-6i,Table I-6, Example 6) gave better results than that extracted with 18%NaOH.

[0091] In comparison to the absorption property data given in Example 5,Tables I-5 to III-5, the absorption test results for the prehydrolyzedkraft Southern pine fiber show that these are within a good range ofabsorbency despite having been bleached to this relatively highbrightness prior to cold alkali extraction.

EXAMPLE 7 Kraft Southern Pine Pulp: Unbleached K Number Interaction

[0092] The accompanying Table I-7, Example 7, illustrates a comparativeseries of kraft Southern pine pulps where unbleached pulp K Number wasvaried (relative severity of pulping—low numbers indicate a more drasticpulping schedule with less lignin remaining in the pulp after pulping).In order to establish the desired pulp property regime and pulpingprocedures, the bleaching of all three unbleached stocks was carried outto equivalent brightness (92% ISO). The bleaching chemicals of chlorine,chlorine dioxide, hydrogen peroxide, oxygen and sodium hydroxide wereused. It is noted that as unbleached K Number increased, resultingabsorption properties after cold caustic extraction improved (lowerabsorption times are better). EXAMPLE 7, TABLE I-7 SAMPLE DESIGNATIONA-7i B-7i C-7i D-7i E-7i F-7i SAMPLE DESCRIPTION Processing BleachedBleached Bleached Bleached Bleached Bleached Pulp Pulp Pulp Pulp PulpPulp Before Cold After Cold Before Cold After Cold Before Cold AfterCold Alkali Alkali Alkali Alkali Alkali Alkali Extraction ExtractionExtraction Extraction Extraction Extraction Wood Species Southern pine→→ → → → → Pulping Process Kraft→ → → → → → K Number, mL 19 — 22 — 30 —COLD ALKALI EXTRACTION Not Used Used Not Used Used Not Used Used AlkaliUsed NaOH NaOH NaOH Solution Strength, % 15 15 15 Temperature, ° C. 3030 30 Time, H:M 0:15 0:15 0:15 Consistency, % 3.0 3.0 3.0 PULPANALYTICAL PROPERTIES 92 — 92 — 92 — ISO Brightness, % MULTIPLE INSULTABSORPTION TEST Absorption times, seconds 1st insult 8.6 6.7 — 5.9 8.95.5 2nd insult 46.3 29.6 — 26.9 41.6 18.8 3rd insult 75.0 45.5 — 39.869.1 33.4

EXAMPLE 8 Sitka Spruce Sulfite Pulp

[0093] In a manner similar to that used for the Southern pine chipfurnish, spruce starting material was sulfite pulped. The sulfiteprocess used was acid sulfite (also known as acid bisulfite) as inExample 5. The unbleached pulp was subjected to cold caustic extraction.Data for the cold caustic extracted pulps treated with 15% and 18% NaOHare shown in Table I-8, Example 8. It is noted that while not allstarting pulps perform at the same level, nevertheless there was asignificant improvement in absorbency after cold caustic solutiontreatment for each of the pulps obtained from this species. Both sprucepulp Samples B-8i and C-8i performed similarly (no significantdifference between 15% NaOH and 18% NaOH extractions). EXAMPLE 8, TABLEI-8 SAMPLE DESIGNATION A-8i B-8i C-8i SAMPLE DESCRIPTION ProcessingUnbleached Pulp Unbleached Pulp Unbleached Pulp Before Cold Alkali AfterCold Alkali After Cold Alkali Extraction Extraction Extraction WoodSpecies Sitka Spruce---------------------------------> Pulping ProcessSulfite---------------------------------------> K Number, mL 31 — — COLDALKALI EXTRACTION Not Used Used Used Alkali Used NaOH NaOH SolutionStrength, % 15 18 Temperature, ° C. 30 30 Time, H:M 0:15 0:15Consistency, % 3.0 3.0 PULP ANALYTICAL PROPERTIES — — — ISO Brightness,% MULTIPLE INSULT ABSORPTION TEST Absorption times, seconds 1st insult70.0 12.2 10.0 2nd insult 43.7 22.3 24.1 3rd insult 64.8 33.6 33.2

EXAMPLE 9 Western Hemlock Sulfite Pulp

[0094] This example illustrates the absorption properties obtained for apulp made from a western hemlock chip furnish by a sulfite pulpingprocess (acid sulfite). Cold caustic extraction of the bleached hemlockpulp (ISO Brightness=88%) again illustrates the improvement that resultson cold alkali treatment: greater speed of absorbency of fibers producedby cold caustic solution extraction. The data are given in Table I-9,Example 9. EXAMPLE 9, TABLE I-9 SAMPLE DESIGNATION A-9i B-9i C-9i SAMPLEDESCRIPTION Processing Bleached Pulp Bleached Pulp Bleached Pulp BeforeCold Alkali After Cold Alkali After Cold Alkali Extraction ExtractionExtraction Wood Species Western Hemlock------------------------------>Pulping Process Sulfite--------------------------------------> K Number,mL — — — COLD ALKALI EXTRACTION Not Used Used Used Alkali Used NaOH NaOHSolution Strength, % 15 18 Temperature, ° C. 30 30 Time, H:M 0:15 0:15Consistency, % 3.0 3.0 PULP ANALYTICAL PROPERTIES 88 — — ISO Brightness,% MULTIPLE INSULT ABSORPTION TEST Absorption times, seconds 1st insult12.3 7.7 9.4 2nd insult 47.2 31.9 39.9 3rd insult 75.1 44.7 62.0

EXAMPLE 10 BCTMP (Bleached Chemi-thermal Mechanical Pulp) and ColdAlkali Extraction

[0095] In this example, BCTMP (a bleached chemi-thermal mechanical pulp)commercially available from Tembec Co. was also extracted with 15% and18% NaOH. The absorption test data (Table I-10, Example 10) showsubstantial improvement at the higher cold caustic solution strength.The K Number of this BCTMP pulp was 36 mL Even higher caustic solutionstrengths (e.g., about 20%) may prove to be beneficial to absorbentproperty performance for fibers produced from this type of furnish viathis pulping process. The wood furnish is a North American, easternCanadian softwood. Description of chemi-thermal mechanical pulping andbleaching processes can be found in texts on pulping and bleaching.EXAMPLE 10, TABLE I-10 SAMPLE DESIGNATION A-10i B-10i C-10i SAMPLEDESCRIPTION Processing Bleached Pulp Unbleached Pulp Unbleached PulpBefore Cold Alkali After Cold Alkali After Cold Alkali ExtractionExtraction Extraction Wood Species NorthernSoftwood-----------------------------> Pulping Process BleachedChemi-thermal mechanical--------------> K Number, mL 36 — — COLD ALKALIEXTRACTION Not Used Used Used Alkali Used NaOH NaOH Solution Strength, %15 18 Temperature, ° C. 30 30 Time, H:M 0:15 0:15 Consistency, % 3.0 3.0PULP ANALYTICAL PROPERTIES — — — ISO Brightness, % MULTIPLE INSULTABSORPTION TEST Absorption times, seconds 1st insult 9.7 8.8 4.0 2ndinsult 39.8 37.8 25.1 3rd insult 61.2 59.8 35.4

EXAMPLE 11 Use of Cold Alkali Extraction on Semi-bleached, LowerBrightness Pulp

[0096] The strength of caustic solution required to achieve optimumabsorption properties is related to the type of raw material and topulping and bleaching steps used. In general, however, the less bleachedflower brightness) the pulp, the higher the concentration of NaOHsolution required to achieve optimum properties. Also, the absorptionproperties attained are better when the pulp is less bleached prior toapplication of a cold caustic treatment. This is illustrated below inTable I-11, Example 11, where two Southern pine kraft pulps bleached todifferent brightness levels (ISO Brightness of 51 and 88, respectively)underwent cold alkali extraction with 15 and 18% NaOH solutions. Theresults for both of these pulps show that 15% NaOH gave the best overallabsorption time results (third insult time is the most significant one)with the pulp of lower brightness (semi-bleached pulp) yielding superiorproperties. EXAMPLE 11, TABLE I-11 SAMPLE DESIGNATION A-11i B-11i C-11iD-11i SAMPLE DESCRIPTION Processing Semi-Bleached Pulp Bleached Pulp(ISO Brightness = 51%)^(a) (ISO Brightness = 88%)^(b) After Cold AlkaliAfter Cold Alkali Extraction-----------> Extraction------------> WoodSpecies Southern pine blend-------------------------> Pulping ProcessKraft--------------------------------------> COLD ALKALI EXTRACTION UsedUsed Used Used Alkali Used NaOH------------------------------------>Solution Strength, % 15 18 15 18 Temperature, ° C. 30 30 30 30 Time, H:M0:15 0:15 0:15 0:15 Consistency, % 3.0 3.0 3.0 3.0 MULTIPLE INSULTABSORPTION TEST Absorption times, seconds 1st insult 5.0 3.8 6.2 4.9 2ndinsult 22.1 21.2 22.2 24.8 3rd insult 25.1 36.7 33.9 38.6 EXAMPLE 11,TABLE II-1 SAMPLE DESIGNATION A-11ii B-11ii C-11ii D-11ii SAMPLEDESCRIPTION Processing Semi-Bleached Pulp Semi-Bleached Pulp (ISOBrightness = 38%)^(a) (ISO Brightness = 44%)^(a) After Cold Alkali AfterCold Alkali Extraction----------> Extraction-----------> Wood SpeciesSouthern pine blend----------------------> Pulping ProcessSulfite----------------------------------> K Number, mL — — — — COLDALKALI EXTRACTION Used Used Used Used Alkali UsedNaOH-------------------------------------> Solution Strength, % 15 18 1518 Temperature, ° C. 30----------------------------------------> Time,H:M 0:15--------------------------------------> Consistency, %3.0---------------------------------------> MULTIPLE INSULT ABSORPTIONTEST Absorption times, seconds 1st insult 4.5 4.5 5.8 4.7 2nd insult24.5 18.8 24.1 20.2 3rd insult 36.4 30.2 41.1 31.2

[0097] All of the Samples A-11i through D-11i (Table I-11, Example 11)were prepared by bleaching the 30 K Number Southern pine kraft pulpdiscussed in Example 5 (Sample A-5i, Table I-5) to the brightness levelindicated, and then cold caustic extracted under the conditionsindicated. Note that in the unbleached state, 18% NaOH resulted inbetter absorption properties and that these absorption times were betterthan those associated with semi-bleached pulps described in Table I-11,Example 11.

[0098] When the 34 K Number unbleached Southern pine sulfite pulp ofExample 5, Table II-5 (Sample A-5ii) was semi-bleached to ISO Brightnesslevels of 38 and 44, respectively, prior to cold caustic extraction with15 and 18% NaOH, 18% NaOH was still required to give optimum absorptionproperties. The results of this work are seen in Table II-11, Example11. Note that less bleached pulp (ISO Brightness=38%) still gives thebest results when extracted with 18% NaOH (Sample B-11ii versus SampleD-11ii); the results, however, are not as good as those observed by 18%NaOH extraction of the unbleached pulp itself with 18% NaOH (see resultsfor Sample C-5ii, Table II-5, Example 5).

EXAMPLE 12 Position of Cold Alkali Extraction in a Multistage BleachSequence

[0099] The benefits of cold caustic extraction in improving absorbencyoccurs regardless of where it is applied in the bleaching sequence(e.g., at the beginning, the middle, or at the very end). In the samemulti-stage bleaching sequence to prepare high brightness pulps there iseven some indication that when the same quantity of chemicals are used,there may be improved absorption properties by applying the stage in themiddle of the sequence. Such an example is now presented in which theonly bleaching variable, in a 5-stage sequence to prepare a fullybleached pulp from the same unbleached stock, was the position of theCCE stage in the sequence; 15% NaOH solution strength was used. EXAMPLE12, TABLE 1-12 SAMPLE DESIGNATION SAMPLE DESCRIPTION A-12i B-12i C-12iProcessing Fully Bleached Fully Bleached Fully Bleached Pulp (5 BleachPulp (5 Bleach Pulp (5 Bleach Stages) with Cold Stages) with ColdStages) with Alkali Extraction Alkali Extraction Cold Alkali in Stage 1in Stage 3 Extraction in Stage 5 Wood Species Southernpine———————————————> Pulping Process Prehydrolyzed kraft—————————————>COLD ALKALI Used———————————————————> EXTRACTION Alkali UsedNaOH———————————————————> Solution Strength, 15————————————————————> %Temperature, ° C. 30————————————————————> Time, H:M0:15————————————————————> Consistency, % 3—————————————————————> PULPANALYTICAL PROPERTIES ISO Brightness, 84 87 84 % MULTIPLE INSULTABSORPTION TEST Absorption times, seconds 1st insult 17.7 14.4 19.2 2ndinsult 44.5 31.2 43.4 3rd insult 67.7 57.2 70.4

[0100] The results shown above (Table II-12) indicate that when CCE wasused in the middle of the sequence (stage 3), the absorption timeresults were clearly better (Sample B-12i) than when CCE was used the1st or 5th stages. It was interesting to note that ISO Brightness of thefully bleached pulp (Sample B-12i) was also improved relative to theother two (i.e. 87 verses 84%.

EXAMPLE 13 Kraft Pulping Reject Material

[0101] In an effort to look at pulp that is even “rawer” or less pulpedthan what normally occurs in conventional full chemical pulpingprocesses, some “knots” resulting from a conventional kraft cook ofSouthern pine chip furnish were cold caustic extracted with 18% NaOH.“Knots” essentially represent pulping reject materials that are poorlycooked (relatively large in size unlike shives and separable from theresulting pulped fibers via equipment loosely termed “knotters”). It wasnecessary to first defiber these knots in a Waring blender and to flatscreen this defibered material to remove reject material still remainingnon-defibered prior to cold alkali extraction with 18% NaOH. The fibershad a very high K number (>50). EXAMPLE 13, TABLE 1-13 SAMPLEDESIGNATION SAMPLE DESCRIPTION A-13i Processing Defiberized Knots(Rejects) After Cold Alkali Extraction Wood Species Southern pine blendPulping Process Kraft K Number, mL (80 mL test) >50 COLD ALKALIEXTRACTION Used Alkali Used NaOH Solution Strength, % 18 Temperature, °C. 30 Time, H:M 0:15 Consistency, % 3.0 PULP ANALYTICAL PROPERTIES ISOBrightness, % — MULTIPLE INSULT ABSORPTION TEST Absorption times,seconds 1st insult  5.4 2nd insult 13.9 3rd insult 25.9

[0102] The multiple insult absorption test results shown in Table I-13,Example 13 indicate that these type of fibers after cold alkaliextraction exhibit good absorption times. The absorption times areequivalent to those of the cold alkali extraction 30 K number unbleachedkraft Southern pine pulp (Sample C-5i, Table I-5, Example 5) and tothose of the cold alkali extracted 34 K Number unbleached Southern pinesulfite pulp (Sample C-5i, Table II-5, Example 5), despite the rawmaterial being essentially a waste material. A cold caustic extractionwould add significant value in turning this waste fiber into a viableabsorbent product.

[0103] It is believed that similar results would be obtained by stoppingthe initial kraft pulping process at a point(s) corresponding to lessdelignification overall and combining mechanical defiberization andscreening steps prior to cold alkali extraction and/or any bleachingdesired to increase brightness (i.e., semi-chemical rather than fullchemical pulping).

EXAMPLE 14 Alkali Source Other Than Sodium Hydroxide: Kraft White Liquor

[0104] A potential source of sodium hydroxide within a kraft pulp millis white liquor used in the kraft pulping process. White liquor is amixture of sodium hydroxide and sodium sulfide. A suggestion is to carryout cold alkali extraction using the alkali present white liquor (WL) asthe source of NaOH; it is also possible that the sodium sulfide presentin the white liquor will have some positive benefits. In Table I-14,Example 14, are presented results of extraction of an unbleachedSouthern pine kraft pulp with 9-18% NaOH in which some or almost all ofthe NaOH requirements in the cold caustic extraction came from the whiteliquor itself (the contribution of sodium sulfide to alkalinity wasignored). For comparative purposes, cold caustic extractions with 9, 15and 18% NaOH solutions were also carried out as controls (Samples F-14i,G-14i, and H-14i, Table I-14). EXAMPLE 14, TABLE I-14 SAMPLE DESIGNATIONA-14i B-14i C-14i D-14i E-14i F-14i G-14i H-14i SAMPLE DESCRIPTIONUnbleached Unbleached Pulp After Unbleached Pulp After Pulp Before ColdAlkali Extraction Cold Alkali Extraction Cold Alkali with White Liquor(WL)^(a) → (Control)→ Extraction Wood Species Southern pine→ → → → → → →→ Pulping Process Kraft→ → → → → → → → K Number, mL 18.7→ → → → → → → →COLD ALKALI EXTRACTION Not Used Used→ → → → → → → Alkali Used (Control)NaOH NaOH NaOH NaOH NaOH NaOH NaOH (96% (67% (48% (37% from from WL)from from WL) WL) WL) Solution Strength, % 9 12 15 18 9 15 18Temperature, ° C. 30→ → → → → → → Time, H:M 0:15→ → → → → → →Consistency, % 3.0→ → → → → → → MULTIPLE INSULT ABSORPTION TESTAbsorption times, seconds 1st Insult 7.0 6.7 6.5 6.5 6.7 8.0 7.0 5.9 2ndInsult 37.2 25.3 23.7 25.0 24.3 30.4 26.1 26.8 3rd Insult 60.7 42.2 37.338.9 37.6 50.5 35.9 37.0

[0105] The use of white liquor to supply alkali was equivalent to theuse of sodium hydroxide at 15 and 18% NaOH solution strength (compareSamples C-14i and G14i, D-14i and H-14i, Table I-14, Example 14) inachieving improved absorption properties relative to those of thenon-cold alkali extracted unbleached Southern pine kraft pulp. At 9%solution strength, the use of white liquor appeared to result in someimprovement over the use of NaOH alone (compare Sample B-14i to F-14i,Table I-14i, Example 14). It is believed that at even lower alkalisolution strengths white liquor may also result in advantages over theuse of sodium hydroxide alone.

EXAMPLE 15 Use of Hemi Caustic for Cold Alkali Extraction

[0106] In using sodium hydroxide for cold alkali extraction, a causticsolution is obtained which contains some organic material removed or“extracted” from the pulp. This type of caustic solution is termed “hemicaustic”. The organic materials solubilized during the cold alkalireaction with the pulp are considered to be predominantly hemicellulosicmaterials (hemicelluloses are non-cellulosic carbohydrate materialscomposed of xylan, mannan, araban, etc. monomers rather than the glucosemonomer of cellulose). For a fibrous end-use pulp, cold alkaliextraction may also remove some of these hemicelluloses or otherorganics. However, the desired end-result is not chemically purer pulpfibers. Purity is required in dissolving pulps because these pulps mustfunction as chemical feedstocks in chemical end-use processes (esterssuch as acetates, butyrates and nitrates, ethers, regenerated cellulose,etc.). For a fibrous end-use application, the end result desired fromthe use of cold alkali extraction is that the fibers produced exhibitimproved performance as fibers—as fluffed fibers in absorbent products,etc. such appreciation of the desired end result heretofore has not beenrecognized or known. EXAMPLE 15, TABLE 1-15 SAMPLE DESIGNATION SAMPLEDESCRIPTION A-15i B-15i C-15i Processing Standard Cold Alkali ExtractionProcess (Bleached Pulp subsequent (Bleached Pulp to Cold Alkali prior toCold Extraction—————> Alkali Extraction) Wood Species Southern pineblend—————————> Pulping Process Kraft———————————————> K Number, mL17.4———————————————> COLD ALKALI Not Used Used———————> EXTRACTION AlkaliUsed (Control 100% 100% hemi NaOH caustic Solution Strength, 15————————>% Temperature, ° C. 30————————> Time, H:M 0:15———————> Consistency, %3————————> PULP ANALYTICAL PROPERTIES ISO Brightness, 84.4 85.5 84.4 %MULTIPLE INSULT ABSORPTION TEST Absorption times, seconds 1st insult 4.7  4.9  4.9 2nd insult 25.6 18.8 20.4 3rd insult 44.8 29.9 36.6

[0107] The data presented in Example 15, Table I-15 show that hemicaustic (i.e., caustic separated from the pulp after reaction under aninitial pure sodium hydroxide cold caustic extraction) can be reused tosupply the alkali source for subsequent cold caustic extractions forpulps with improvements in absorbency properties. Absorption times areimproved relative to the non-cold caustic extracted bleached Southernpine kraft pulp when the alkali source used was either sodium hydroxideor hemi caustic. The hemi caustic solution used was at 24.5% sodiumhydroxide by weight and contained 2.9% “hemicellulose” material. Theimprovements when the hemi caustic was used were not as great as thosewhen pure sodium hydroxide was used. However, it is expected that somemodification of the cold caustic extraction conditions (for example,increasing the solution strength when hemi caustic is used) would makethe effects of both types of caustic equivalent.

[0108] It would also follow that other alkali sources when used ininitially contacting the pulp in a cold alkali extraction could bereused in subsequent extraction for these types of fibrous end-usenon-dissolving pulps.

[0109] In the above Examples the cold caustic solution treatment or coldcaustic extraction of the pulp was typically at the indicated solutionstrength, at 3.0% consistency, for 15 minutes at 30° C., followed by afresh water rinse (30° C.), an acid wash (typically a sulfuric acidsolution at pH of about 3) and a final fresh water rinse.

[0110] Other test data that were obtained also indicate that for theentire range of concentration of the cold caustic solution, theconcentration may range between about 5% to 25% and higher but 13% to18% gave the best results for the various pulp starting materialsutilized for acquisition layers, i.e. intensive, fast absorption uses. Asuitable concentration is dependent on the relative severity ofbleaching with the more severely bleached pulps requiring a mildertreatment. For absorbency improvements in general and also for improvingyields and other fluff pulp properties lower concentrations of causticmay be used i.e. to about 5%. The versatility of the process has alsobeen demonstrated for a variety of pulp source materials.

[0111] As illustrated above and while in the examples the cold causticsolution has been a sodium hydroxide solution, other alkali materialsmay be used. Other alkali materials such as potassium hydroxide etc. maybe used but at a severe economic penalty such that their use isprohibitive.

[0112] Likewise, a combination of sodium hydroxide solution and a watersoluble, non-toxic glycol, (e.g., propylene glycol solution) might alsobe used, but the added cost is less justified for this large volume bulkproduct.

[0113] In describing the regime for the acceptable starting pulps andprocess conditions for CCE treatment, this regime may be characterizedas follows: for fast absorbency improvements such as measured by theinsult tests, especially the third insult, the K Number related toabsorbency and severity of pulping, the severity of pulping which may beavoided when practicing the present utilization of various pulps inbleached and unbleached conditions, enhanced yields and advantageous useof reject materials, use of mill by-products, swing capability to insertin the bleaching treatment steps the CCE step in any bleaching sequence,fluff pulp properties not requiring debonders, i.e. without additives,etc. etc. Such improvements especially in combination with each otherhave heretofore not been recognized, known or practiced for fluff pulpsand thus have not shown the way to the unique combination(s) ofproperties described above.

[0114] The basis weight of acquisition layers in current products rangesfrom 75 to 200 g/m². As an example, the acquisition layer 12 shown inFIG. 2 is an air laid fluff web of 200 g/m². This web is separated fromthe absorbent core 13 by a layer of conventionally wet-laid tissue paper13. The core may be wrapped in such tissue paper. The absorbent core isa mixture of cellulose fiber, fluffed and airlaid with super absorbentpolymer (SAP) available from commercial sources. The basis weight isabout 500-700 g/m². There is a moisture proof polymer backsheet 16 belowthe core of 0.5 mil. Wet laid sheets may also be used.

[0115] The above described examples, embodiments, and comparisons areintended to illustrate the various aspects of the invention withoutlimitation of same but the appended claims and elements thereofincluding reasonable equivalents for these are to define the metes andbounds of the invention.

What is claimed:
 1. In a process for improving the characteristics of apulp useful for making a fluff pulp or a pulp for absorbency intensiveapplications the improvement comprising: treating a pulp at atemperature of up to about 60° C., in a suspension, with an alkalisolution of a concentration from about 2% to about 25% by weight, for atreatment time sufficient to obtain a pulp of improved absorbencycharacteristics, and recovering said thus treated pulp from saidsuspension suitable for intensive absorbency and fluff pulp useapplications.
 2. In a method for improving absorbency of pulps andincreasing yields thereof the improvement comprising: subjecting a pulpfiber suspension at a temperature of less than about 45° C., in a fibersuspension from about 2% up to about 25% consistency, to a causticsolution of a concentration of about 5% to 25% by weight for a timesufficient to improve the absorbency characteristics of a pulp materialresulting from such treatment.
 3. In a process for improving pulpproperties of pulps useful as fluff pulps the improvement comprising:subjecting a pulp fiber suspension at a temperature of less than about45° C., in a fiber suspension from about 2% up to about 25% consistency,to a caustic solution of a concentration of about 5% to 25% by weightfor a time sufficient to improve the absorbency characteristics of apulp material resulting from such treatment.
 4. The process as definedin claim 3, and wherein the temperature of said pulp fiber suspension isless than about 40° C., the fiber suspension is from about 2% to 10%consistency, and the caustic solution is at a concentration from about5% to about 18% by weight.
 5. The process as defined in claim 3, whereinthe concentration of said caustic solution is between 13% and 15% byweight.
 6. The process as defined in claim 3 wherein the concentrationof said caustic solution is between 5% and 10% by weight.
 7. The processas defined in claim 3, wherein said pulp is from a pulp source startingmaterial of Southern pine, White pine, Western hemlock, a Sitka spruce,Caribbean pine, a Douglas fir or mixtures of same.
 8. The process asdefined in claim 3, wherein said pulp is from a pulp source startingmaterial of eucalyptus, poplar, beech, aspen or bagasse.
 9. The processas defined in claim 3, wherein the temperature of said caustic treatmentis about 30° C. and a time of treatment is from about 5 minutes to aboutone hour.
 10. In a process for improving the fast absorbencycharacteristics of a pulp useful in absorbency intensive applicationsthe improvement comprising: treating pulp at a temperature of less thanabout 40° C. in a suspension with a caustic solution of a concentrationfrom about 13% to about 18% by weight, said concentration beingdependent on the amount of lignin remaining in the pulp, as measured bythe K number and a severity of pulping of said pulp, for a treatmenttime sufficient to obtain a pulp of improved absorbency, and recoveringthe thus treated pulp from said suspension suitable for intensiveabsorbency and fluff pulp use applications.
 11. The process as definedin claim 10, wherein said pulp is an unbleached pulp with a K number of8 or above before the same is treated with caustic solution.
 12. Theprocess as defined in claim 10, wherein said pulp is partially bleachedbefore treatment of same with said caustic solution.
 13. The processdefined in claim 10, wherein the pulp is a chemical-mechanical pulp ororganic solvent obtained pulp.
 14. The process as defined in claim 12,wherein a bleached pulp is a kraft process pulp, before said pulp istreated with said cold caustic solution.
 15. The process as defined inclaim 12, wherein said bleached pulp is treated with a caustic solutionof a concentration inversely proportional to a severity of bleaching towhich said pulp had been subjected and wherein said pulp maintains itsimproved absorbency characteristics upon rewetting.
 16. The process asdefined in claim 10, wherein said absorbency intensive application isfor an acquisition layer for a baby diaper.
 17. The process as definedin claim 10, wherein a pulp source starting material is a pulp derivedfrom a softwood.
 18. The process as defined in claim 10, wherein saidpulp is bleached prior to its treatment with a caustic solution to anISO brightness percentage of about 25 and higher.
 19. The process asdefined in claim 10, wherein said pulp is treated with a causticsolution in a suspension of about 3% by weight (O.D.) pulp at atemperature from about 25° C. to about 40° C. for a period of timesufficient to improve said absorbency for said pulp.
 20. The process asdefined in claim 10, wherein pulps of low K number of at least 12 aretreated with a caustic solution of a concentration of up to about 15%.21. The process as defined in claim 20, wherein the concentration ofsaid caustic solution is between 13% and 15% by weight.
 22. The processas defined in claim 10 wherein said pulp is from a pulp source startingmaterial of Southern pine, White pine, Western hemlock, a Sitka spruce,Caribbean pine, a Douglas fir or mixtures of same.
 23. The process asdefined in claim 10, wherein said pulp is from a pulp source startingmaterial of eucalyptus, poplar, beech, aspen, bagasse or mixtures ofsame.
 24. The process as defined in claim 10, wherein the temperature ofsaid caustic treatment is about 30° C. and a time of treatment is fromabout 5 minutes to about one hour.
 25. In a process of constructing anabsorbent device having an outer acquisition layer and an innerabsorbent core element, the improved process comprising: pulping a pulpsource starting material to a preselected K number of about 8 and aboveto obtain a pulp with substantially said K number and wherein said pulpis optionally bleached; treating said pulp at a temperature of less thanabout 45° C. in a suspension with a caustic solution of a concentrationfrom about 5% to about 25% by weight, with a treatment time sufficientto obtain a pulp of improved absorbency values, and recovering thustreated pulp from said suspension suitable for absorbency applicationsin said device; sheeting and drying said pulp into a sheet of a basisweight from 200 to 800 grams per meter squared; and converting saidsheet to an outer layer for said diaper on at least one surface of acore element of said device or a core element for said device.
 26. Theprocess as defined in claim 25, wherein said core element is composed atleast in part of improved absorbency pulp obtained as defined in claim25 derived from Southern pine pulp.
 27. The process as defined in claim25, wherein the device is a baby diaper.
 28. The process as defined inclaim 25, wherein the device is a catamenial device.
 29. The process asdefined in claim 25, wherein the device is an incontinence device. 30.The process as defined in claim 25, wherein an absorbent pulp componentis of a pulp obtained from hard wood pulp.
 31. The process as defined inclaim 25, wherein the absorbent pulp is of a pulp from Western hemlock.32. The process as defined in claim 25, wherein sheeting and drying saidpulp is after flash drying and collecting of said pulp.
 33. An improvedpulp for an absorbent device comprised of at least an acquisition layerelement wherein said layer is of a pulp as defined in claim
 10. 34. Animproved absorbency material comprised of a cellulosic fibrous materialwherein said cellulosic fibrous material has been obtained by pulping acellulosic source material which has an unbleached pulp K number of atleast 12 and wherein said cellulosic fibrous material is a cold causticsolution treated material at a treatment temperature of less than about40° C., in a suspension of 2% to 15%, with said cold caustic solutionbeing at a concentration of from about 5% to 25% by weight.
 35. Theimproved absorbency material as defined in claim 34 wherein thecellulosic fibrous material subsequent to cold caustic treatment hasbeen mechanically treated.
 36. The improved absorbency material asdefined in claim 34 wherein the cellulosic fibrous material subsequentto cold caustic treatment has been beaten.
 37. The improved absorbencymaterial as defined in claim 34 wherein the unbleached pulp K number forsame is at least about 20 and above.
 38. The improved absorbencymaterial as defined in claim 34 above wherein the same is incorporatedinto a baby diaper, a catamenial device, an incontinence device, a towelor a tissue in sheet form.
 39. In a process for improving the absorbencyof a cellulosic material in a fibrous form of said cellulosic materialwherein said material is useful in absorbency applications, theimprovement comprising: treating said cellulosic material at atemperature of less than about 45° C., in suspension, with a causticsolution of a concentration from about 5% to about 10% by weight, saidconcentration being dependent on the process employed, wood species usedand/or on the amount of lignin remaining in said cellulosic material asmeasured by a K number measurement, wherein said caustic solution is incontact with said cellulosic material for a treatment time sufficient toobtain a cellulosic material of improved absorbency values, andrecovering thus treated cellulosic material from said suspensionsuitable for absorbency applications.
 40. The process as defined inclaim 39, wherein said cellulosic material is an unbleached pulp with aK number of at least about 8 or above before treatment of same with saidcaustic solution.
 41. The process as defined in claim 39, wherein saidcellulosic material is a partially bleached pulp before treatment ofsame with said caustic solution.
 42. The process as defined in claim 39,wherein the cellulosic material is a bleached pulp, before treatment ofsaid pulp with said cold caustic solution.
 43. The process as defined inclaim 41, wherein said bleached pulp is treated with a caustic solutionof a concentration inversely proportional to a severity of bleaching towhich said pulp had been subjected and wherein said pulp maintains itsimproved absorbency characteristics upon rewetting.